However, many of the children reportedly tried to swim across the fjord (lake?) to shore (the camp is on an island) and reports are still confused regards a second gunman at the camp so this could get worse still.

UPDATE: It seems that it was a xenophobic lunatic. It looks like he acted alone, but I would not rule out at least tangential involvement of others. He left 85 dead at the youth camp alone. Posing as a cop, he called everyone out into a large area and shot them. Sick.

Note that while I am pleased I did refrain from jumping to conclusions on this one, in defense of the bloggers who were pretty sure it was islamists, the facts at the time did seem to strongly support that theory.
*There had been a claim of responsibility by a muslim group.
*There is a current issue with the arrest of a radical cleric.
*There had been threats regarding that arrest.
*This looked like Mumbai, and the African embassy bombings combined, particularly with the cop impersonation (the Mumbai killers used ambulances for transport)
*I can't think of anything like this in Europe aside from the leftist bombings of the 70's/80's.

To their credit, virtually all of those bloggers amended their coverage as soon as the facts became apparent.